Pulse communication



Jan. 1l, 1949. o. E. Dow

PULSE COMMUNICATION Filed April l0, 1943 #SGR ESS @S Q Janna m59 N0 39h/170A N, Sm

@lV/70H9 U/Vl?l l .750!!0 300K/V3 NIJ/M136 '.7917270/1 INVENTOR OHV/LE E. DOW p ATTORNEY Patented Jan. 171', 1949 VU it! l TED .S TATTES PT-EINT Fl CIE PULSE COMMUNICATION Orville E. Dow, kjlRocliy Point, 'N. Y., .assignor"to Radio Corporation of Americafa corporatonof Delaware Applicationy Aprilfl, 1943,I.Seriall`=No.54825578 20 Claims. 1

This invention relates toirnprovements in.pulse type communication systems, andparticularly .to a method of .and `apparatus 4for-generating short duration pulses-and .ier-.modulating the repeti- -tion rate or frequency of these-pulseslin` accordance Ywith thensignalto be transmitted. `Inone aspect, .the present invention providesmeansffor efciently producing .and modulatingultra high frequency pulses of theor-derof onemicrosecond duration andlonger.

.An important featureoi thepresentin lention -lies in .the use of a Aregenerative vacuum tube .pulse generator in whosecathode. circuit is a line whose electrical length determinesthe-duration of the pulseto begenerated. This'. line maybe any suitable type but is .preferably `an .articial 'line inthe form .of a low pass `"filter Y.consisting of several sections. "Another'feature .ofthe invention includes the .use of a modulating tube placed acrossthe line inthe cathode circuit ,of l

total time. Another advantage of .theirvention` is-tha'tlthe system is very' stable inipulselength at the extremely short "pulse y'duration intervals employed. n

Otherieatures and advantages ofthe 'invention will appear from a-reading ofthe following description Awhich `is accompanied by 'a drawing wherein:

Fig. l diagrammatically illustratesone"embodiment of the inventionas applied to "anultra --short wave radio puls-etransmittingsysteimand Fig. 2 graphically 'illustrates i thev operation fof the pulse generator `ofFig. 1.

Referring to the'transmitting system'of Fig. 1 'in-more detail, tliereis shown afpulse igenerator in the form of a vacuum tubepentodelwhose control grid-and anode 'electrode areconnected to separate windings I I and I2, respectivelxof athree winding pulse'itransformerTR. JWinding It of the pulse transformer 4derives "rectangular "lating Vsignal maybej'speech or any other suitable signal.

former-"4.

Gfandllfand a-'ShuntcOnnected condenser 8 and .,these: pulses by way'rof fier=l Il` forcontrollingA` a suitable ultra short `wave generator -sueh nasza magnetron `'I I. -shape of these rectangular wave pulses is Ashown rimmediately @above ...lead HI. .-The .pulse :translead I4 -to a pulse ampliformer isso coupled to the-pentode I that there f s 1 a regenerative .action .which gives very sharp increase ofcurrentin the tube I when the current islbuilding'lup, and .ver-y sharp-decay when the current is decreasing, thus zproviding Vpulsesrof Vsharp .slopes or edges.

Infcircuit with the cathodeof .the `pento'de an artificial line L, Voneend .of .which is-connected between the cathodeand ground, as shown, and ythe otherend of .-whichis connected across a constant current modulator l.pentode vacuum tube2. `In practice, `the modulator tube maybe placed anywhere along the lengthof the line'L and even at the cathode end, if so desired. The

'lineis shown in 'the form `ofalow pass 'filter consisting of severalsections, butmay be .any suitable'type. .A coaxial lineis notbelieved'to 'be `desirable for practical reasons because it woul'd/betoolong and'bulky comparedto more compact available structures. The'internal plate impedance'ofthe modulating Ytube is designed'to be'liigh compared to the characteristic impedance of 'the -line L. 'il'signal modulating circuit'is coupled across' the "control grid and cathode of tube Zithrough an audio `amplifier 3. "The'modu- The heater ofthe pulse generator tube Iis supplied with fheating energy'from a'low frequency powersupplythrough aniron core trans- ""Tlie'anode of ytubel is-supplied with va positive AThis same power supply furnishes tor tube'Zthrough an arrangement'which serves toA maintain the pulse repetition rate or frequency independent -of Asupply voltage variations of EB. rIhis arrangement includes-a pair of series resistors will "be furtherdesci'ibed later.

fCondensersfCfandCi are by-pass condensers "for the screengridsI of tubes `I and 2 respectively. Condenser C1 is aby-vpass condenser for the pulse frequency to fm'aintain the `ylscreen grid of tube 2 at-constant potential as far as-pulse voltages are concerned. The dotted line resistor Rsg in shunt iso-'condenser= C1A represents internal impeclencel to 1Jwave outputpulses of short durationandisupplies ltoground of thescreen grid lof the Amodulator 3 tube 2. At this time it should be noted that the cathode of tube I is always maintained at a positive potential relative to ground, and supplies the anode voltage for the modulator tube 2 through the line L.

In the operation of the system of Fig. l, an increase of current through the winding I2 will induce a voltage in winding II in such direction as to place a positive pulse on the control grid which will hasten or expedite the flow of current through tube i. The flow of current through tube I will cause a pulse of voltage to flow down line L from the cathode end to the other end at which the modulator tube 2 is located. When this traveling pulse of voltage reaches the last end of the line, it will be reflected in phase and travel back along the line L to the cathode of tube I with a resultant voltage eiTectiv-ely double the initial voltage. When this resultant voltage reaches the cathode end of the line, it cuts off the current through the tube I. The initial pulse voltage produced at the cathode end of the line L due to current flowing in tube I is of such relative polarity as to tend to cut down the current flow in the tube but is not of suflicient magnitude at this time to cut off the conductivity of the tube. But when the pulse returns to the cathode from the other end of the line with a resultant magnitude of twice the initial magnitude it is then of suiicient value to decrease the current owing through the tube. When the current starts to decrease through the tube and through winding I2, the voltage induced in winding II by this decreasing current will reduce the positive voltage on the grid and hasten the cut oif action. This regenerative action serves to give very sharp decay and very sharp increase of current in the tube.

The operation of the pulse generator I is graphically illustrated in Fig. 2, wherein graph (a) shows the variations in the voltage between the cathode of tube I and ground with resp-ect to time, and graph (b) illustrates the variations in the Voltage on the control gride of tube I with respect to time. Point X on the ordinate of graph (a) is the cut off voltage on the tube I. The distance Y on graph (a) represents the instantaneous value of voltage across the cathode end of the line L at any instant, as measured from the slope of the curve to the zero voltage line. Time t1 represents the time during which no current flows in the tube I, while time t2 represents the time of each pulse during which current does flow in tube I. It will be seen that the duration of the pulses is very short compared to the time interval between them. The saw-tooth voltage wave of graph (a) appears between the cathode and ground, while the rectangular wave of graph (b) appears in the output circuit of the pulse generator I and is available in winding I3.

The effect of the pulse traveling down the line L and back again is to charge up the capacity in the line to a value equal to the resultantvoltage. This voltage on the line capacity will keep the tube I cut off until the voltage in the line dissipates to a value below the cut-01T value of the tube I. This dissipation occurs through the modulator tube 2 and the time thereof may be increased or decreased by means of modulating potentials applied to the control grid of tube 2. The control grid of the modulator tube controls the effective impedance of the tube 2. Modulator tube 2 provides a constant current ow therethrough for any Xed value of bias on the control grid thereof.

In order to prevent variations in voltage of source EB as applied to the anode of tube I from changing the pulse rate or frequency, due to variations of voltage across the line L, the screen grid voltage of the modulator tube 2 is varied in phase with the variations in the voltage on the anode of tube I. The screen grid voltage for tube 2 is supplied through series resistors I5 and l. In order for the foregoing in-phase relation to be maintained for rapidly varying voltages, such as power supply ripple voltages, in the anode supply EB, the RC or the time constant of circuits 6, 'I and 8 should be equal to the RC of circuit Rsg, C1.

The plus voltage supplied to the screen grid of tube I is maintained constant by a voltage regulator such as the RCA VR--30, or other suitable regulator. Because the voltage applied to the anode of this tube is much higher it is not desirable to regulate it in a similar manner.

This last feature may be further explained as follows: When the positive voltage on the anode of tube I increases, there is a larger positive voltage placed on the line L which must be dissipated faster if the same pulse repetition rate is to be maintained. By also increasing the screen voltage on modulator tube 2 at this time, there will be an increase of current through tube 2 and an increased rate of dissipzltion of the line voltage. On the other hand, a decrease in the positive voltage on the anode of tube I will be accompanied by a decrease in voltage on the screen grid of tube 2 with a concomitant decreased rate of dissipation of the line voltage.

The use of a constant current pentode for the modulator tube 2 has the advantage of permitting the instantaneous pulse frequency to be more constant because the slope of the saw-tooth wave (a) of Fig. 2 will intercept the cut-off line X at a steeper angle than would the curved line (shown dotted) which would result if the modulating device across the line acted as a constant resistance. It will be evident that variations in modulating potential applied to the control grid of tube 2 will vary the impedance of the tube 2 with a consequentvariation in the dissipation rate of the voltage on line L. As a result of this, the pulse rate will be varied in dependence upon the modulating potentials.

As for the ultra high frequency oscillator II, this is shown, diagrammatically only, as a magnetron having a cathode connected to the pulse amplifier I0 and a surrounding anode connected to ground.

A magnetic coil producing flux lines substantially parallel to the axis of the cathode of magnetron II is shown in dash lines. Output from the magnetron is taken from a loop located in the interior of the magnetron (as shown) and connected to a lead I5 extending to the antenna. This magnetron will be pulsed by the rectangular wave form short duration pulses impressed thereon by the pulse generator I to produce corresponding length pulses of ultra short wave energy which are radiated from the antenna, not shown. The wave form of these short Wave pulses is shown above lead I5, Thus, microsecond duration pulses generated by the pulse generator will control the ultra high frequency oscillator to produce microsecond pulses of ultra short wavelength energy.

The term ground used in this specification and the appended claims is deemed to include any point or surface of zero radio frequency potential.

What is claimed is:

S "1. In a radio systemhavingianlectron I`l`'discharge `device, `a Y pulse -fge'nerator provided with Va-"catl-iode, fand a line ffpre'dterminedlength having two ends,'lsaidline 'being connected atfone endbetween said` cathodef-and-ground, method of :generating 'a :trai-n -of-'pulse's Lwhich :are each of .short duration compared to #the ftime .interval 'between them, which includes initiatin'glva'voltage -wavelatth'e vcathode fen'diof said'l line: atj the start of current flowin said-:devicesreflecting said `wave Ifrom :'thefother1 end-"of thellirlev inea4 cophasal relationbwith'- the wave-inrSt-'tra'velin'gdown the line :to produce aresultantivoltage of vla rmagnitude vapprecialoly lgreater than `the initial voltage -and vinsuch sense as l"tofco'mpletelyextinguish the rpulselat the jtime theA reileetedziwavel reaches said cathode en'd 'of fthe line, tto i thereby #charge f the capacityA ofthe'- line :atithe value of said 'resultant lvoltage, :and dissipating .zsad voltage vcharge on 'theline iin .accordance with 'modulatin'glpoten- "vtials, whereby Lthe reptition rate fof the pulses generated by said device varies as -=a"functional relation to saidfmodulatingfipotentials.

2. Afpulseregenerative'oscillator comprising an electron discharge *device having'a cathode, v`an anodenzar-idv a control g-rid,separateicoils. in circuit with -saidianode and gridwwhichfare coupled to =each other, and aline :of predetermined length vvconnected atoneend between said cathode and J ground and terminated-'ati its other end such that a voltage wave traveling-downtheflinefrom the 'cathodefend'vwill be re'flectedffrom said other end vin-phase to @produce a :resultant voltage onsaid 1line effectively substantially Adouble the finitial voltagefwave.

3. 'A spulse :regenerative oscillator kcomprising an electrondischarge device :having a cathode, -an vanode and a vcontroligrid, separate coils lin circuit with said anode and grid whichiare coupled toreach other, ai `line of. predetermined! length connected at one iend :loetwe'en ..said=cathode :and

ground 'andfterminated atgits -other end such Ithat a voltage Waveitravelingdown the line from the vcathode enirwil-lzbei reflected fromsaid other end in-phase'toproducefaresultant voltage on said line eieotively `lsulostantially double the 'initial ;voltage wave, :ar-modulator coupled across -said line,l and rneansf for :varying:theiconductivity Voi-said modulatorinaccordance withsa signal.

4. :A :pulse :regenerative .ioscillator ..'comprising -an Yelectron 4l.discharge device Ahaving a ncathode, v.and :anode and; afcontrol ngri'd, :separatev coils in circuit with said anode and 'grid' which 'are coupled .to each `other, :a line of predetermined ,i length connected'fat one-fend betweenfsai'd cathode and saidl line, and means forfapplyingaudio frequency modulating potentials 'to` said i modulator to vari7 the conductivity thereof fin-,accordance with a signal to be transmitted.

5. A pulse Iregenerative oscillator comprising an electron discharge device havinga cathode,

ran anode=and a -control grid, separate coils in circuit With said anode'and grid which are coupled to each other, la line of predetermined length connected. at one end betweenrsaid cathode :and .f ground and terminated atiits `other-,end such ,-thatza voltage lwave- `traveling-` down fthe line from 6 ther'cathode V-end fwill'hefriiected s'freinsaiilfother endiin-#phase-"to Vpred'uce afre'sltant-vltage on said `line effectively t`snltstarltially Adouble fthe initial voltage wave, 'a source otanodepolari'zing potential Iforithe'ano'deff -saiddevicepa--mo'du lator in the v"or-ndfof 1=a screen `grid lelec-tron discharge `device f coupled across-` saidf' line means for applyingmodulatingfpotentialsftolsaidfmodulator, and a connectionfrem theds'creengrid f'fsaid modulator devicelr to ysaidj sourcetoivary therscreen potential in -phase with the v-*voltage'i fluctuations of said source,fsaitlfconnectionf including `at least one resistor.

`I-6. pulse :regenerative oscillator comprising an i electron f discharge `device I' having a cathode, 4anfanodefand 4a controlfgri'd,fseparate coilsn circuit with said anodeland-grid whichfareicoupled tc eachother, a line `(if predetermined length connected at onelendbetweensaid cathodeand ground Aand terminated lfat Lits 'other end y such thata v'voltage waveitraveling doWn-thel line 'from the cathode endqwill Alee. reflected fromz saidf other en'd in-phase to --produce ai lresultant l-volta'gefon `denser and screenigridgtorground resistance.

v'7. -A :pulse AYregenerative zoscillato'r Ycomprising an electron discharge 'device :having :a cathode, `an anode and -a control rgrid, :separate -y coils iin circuit with 'said anode landglgri'd ywhichv are coupled to each other, a line-offpredetermined'length connected at-one end betweensaidfcathodeY and ground vand terminated at its lother:e1i1d .isuch that a voltagelwave traveling downl thelline from the cathode end will be reflected-fromv saidother end in-phase tonproduce aaresultant'voltageon said line effectively substantially double fthe initial voltage `wave, ,anotherK coil coupled to said irst coils for deriving the ,output fromfsaid pulse oscillator, and anultra high; frequency oscillator coupledto said other coilvandresponsive tothe pulses'therein for lproducing,ip ulses:of ultra high frequency energy.

8. A ypulse Aragenerative oscillator comprising an r electron discharge l device having :a cathode,

`an anode andi/a control lfgrid, :separatecoils Ain circuit withisaid. anode and grid which are coupled to eachother, and aline lof predetermined length connected at one end between said cathodeand ground and terminated 'at its v`otherend such 'that a-voltage wave traveling downthe line from `said line in accordance .-witha. signal.

9. Apulse regenerative oscillatorcomprisingan electrondischarge device Vhaving `:a cathode, ..-an anode and :a: control grid, rseparate coils lin circuit with said anode and grid which are coupled to each other, and an articial line of predetermined electrical length connected at one end between said cathode and ground and terminated at its other end such that a voltage wave traveling down the line from the cathode end will be reflected from said other end in-phase to produce a resultant voltage on said line appreciably greater than the initial voltage wave.

10. A pulse regenerative oscillator comprising an electron discharge device having a cathode, an anode and a control grid, separate coils in circuit with said anode and grid which are coupled to each other, a line of predetermined length connected at one end between said cathode and ground and terminated at its other end such that a voltage wave traveling down the line from the cathode end will be reflected from said other end in-phase to produce a resultant voltage on said line appreciably greater than the initial voltage wave, a modulator coupled across said other end of said line, and means for varying the conductivity of said modulator in accordance with a signal.

11. A pulse regenerative oscillator comprising an evacuated electron discharge device having a cathode, an anode and a control grid, separate coils in circuit with said anode and grid and which are coupled to each other, means for determining the duration of the pulse to be generated including a line of predetermined electrical length coupled at one end to an electrode of said device and terminated at its other end in such manner that a voltage wave traveling down the line from said electrode end will be reflected from the other end in such phase that the flow of current in said device will be extinguished when said reflected wave arrives at said electrode.

12. A pulse regenerative oscillator comprising an evacuated electron discharge device having a cathode, an anode and a control grid, separate coils in circuit with said anode and grid and which are coupled to each other, and means for determining the duration of the pulse to be generated including a line of predetermined electrical length coupled at one end to said cathode of said device and terminated at its other end in such manner that a voltage wave traveling down the line from the cathode end will be reected from the other end in such phase that the now of current in said device will be extinguished when said reflected wave arrives at said cathode.

13. A pulse oscillator comprising an electron discharge device having a cathode, means in circuit with said oscillator for causing said oscillator to produce recurring pulses of electrical energy, said means including a line of predetermined length connected at one end between said cathode and ground and terminated at its other end in a relatively high impedance compared to the characteristic impedance of the line such that a voltage wave traveling down the line from the cathode end will be reflected from said other end in-phase to produce a resultant Voltage on said line appreciably greater than the initial voltage wave.

14. A pulse regenerative oscillator comprising an electron discharge device having a cathode, an anode and a control grid, separate coils in circuit with said anode and grid which are coupled to each other, and a low pass lter in the form of an articial line of predetermined electrical length connected at one end between said cathode and ground and terminated at its other end by an impedance which is high compared to the char- 8 acteristic impedance of said line such that a voltage wave traveling down the line from the cathode end will be reflected from said other end inphase to produce a resultant voltage on said line appreciably greater than the initial voltage wave.

15. A pulse regenerative oscillator comprising an electron discharge device having a cathode, an anode and a control grid, separate coils in circuit with said anode and grid which are coupled to each other, a line of predetermined length connected at one end between said cathode and ground and terminated at its other end such that a voltage wave travelingl down the line from the cathode end will be reflected from said other end in-phase to produce a resultant voltage on said line appreciably greater than the initial voltage wave, a modulator coupled across said other end of said line and having an internal plate impedance which is high compared to the characteristic impedance of said line, and means for varying the conductivity of said modulator in accordance with a signal.

16. A pulse regenerative oscillator comprising an electron discharge device having a cathode, an anode and a control grid, separate coils in circuit with said anode and grid which are coupled to each other, a line of predetermined length connected at one end between said cathode and ground and having a high impedance at its other end such that a voltage wave traveling down the line from the cathode end will be reected from said other end in-phase to produce a resultant voltage on said line appreciably greater than the initial voltage wave, a modulator coupled across said line and having an internal plate impedance which is high compared to the characteristic impedance of said line, and means for varying the conductivity of said modulator in accordance with a signal.

1'7. A pulse oscillator -comprising an electron discharge device having a cathode, a line of predetermined length connected at one end between said cathode and ground and having a high impedance at its other end such that a voltage wave traveling down the line from the cathode end will be reflected from said other end in-phase to produce a resultant voltage on said line appreciably greater than the initial voltage wave, a modulator coupled across said line and having an internal plate impedance which is high compared to the characteristic impedance of said line, and means for varying the conductivity of said modulator in accordance with a signal.

18. A pulse oscillator comprising an electron discharge device having a cathode, a line of predetermined length connected at one end between said cathode and ground and being open at its other end such that a voltage wave traveling down the line from the cathode end will be reflected from said other end in-phase to produce a resultant voltage on said line appreciably greater than the initial voltage wave, a vacuum tube coupled across said line and having an 'internal plate impedance which is high compared to the characteristic impedance of said line, and means for varying the conductivity of said vacuum tube in accordance with a signal.

19. In combination with an electron discharge device magnetron having a cathode, a surrounding anode structure, means for producing a magnetic field parallel to said cathode, a connection from said anode to ground, a pulse oscillator supplying said cathode with recurring rectangular wave form pulses of positive polarity and equal duration and of steep starting and trailing edges.

said pulses having a magnitude sufficient to cause said magnetron to produce correspondingly positioned pulses of high frequency energy solely during the time intervals of said pulses, and an electron discharge device modulator coupled to said pulse oscillator for varying the spacing between the equal duration pulses supplied to said magnetron in accordance with modulating potentials.

20. In combination with an electron discharge device magnetron having a cathode electrode and a surrounding anode electrode, means for producing a magnetic field parallel to said cathode, a connection from one of said electrodes to ground, a pulse oscillator supplying said other electrode with recurring rectangular Wave form pulses of positive polarity and equal duration and of steep starting and trailing edges7 said pulses having a magnitude suicient to cause said mag netron to produce correspondingly positioned pulses of high frequency energy solely during the time intervals of said pulses, and an electron discharge device modulator coupled to said pulse 10 oscillator for varying the spacing between the equal duration pulses supplied to said magnetron in accordance with modulating potentials.

ORVILLE E. DOW.

REFERENCES CITED The following references are of record in the file of this patent:

lo UNITED STATES PATENTS Number Name Date 2,212,173 Wheeler et al Aug. 20, 1940 2,221,666 Wilson Nov. 12, 1940 2,252,293 Ohl Aug. 12, 1941 l5 2,255,839 Wilson Sept. 16, 1941 2,266,154 Blumlein Dec. 16, 1941 2,301,160 Finch Nov. 3, 1942 2,405,079 Tonks et al July 30, 1946 2,416,718 Shockley Mar. 4, 1947 FOREIGN PATENTS Number Country Date 479,935 Great Britain Feb. 14, 1938 

